hi I was the one who made that comment. The JSON incompatibilities I was referring to at that time was for an older version of the JSON proposal. The current version of the JSON operator in SQLite mimics Postgres (and MySQL) perfectly and I'm very happy about that.
In the older version of the proposal, -> was identical to ->> except -> returned NULL on malformed JSON (while ->> raised an error). Both -> and ->> would automatically convert a JSON-encoded SQL string '"like this"' into an SQL string 'like this'. This is not how the -> operator behaves in Postgres and MySQL, and my examples were simply trying to point out that incompatibility.
https://sqlite.org/forum/forumpost/a0d681bb2432eebc